We are running Exchange 2003 SP2 and our clients have Office 2010. Our Outlook profiles are created automatically by using Group Policy to set a registry key which points to a PRF file with all the Outlook settings. Lately, many of our users are reporting that their emails are getting stuck in the Outbox. If you look at their Outlook profile, they have two Exchange accounts listed. You cannot delete either of them; it gives a message that this is the default email account.
 
The immediate solution is to recreate the user's Outlook profile. This allows the stuck email to send. The real issue is that this keeps occurring. Recreating the Outlook profile sometimes fixes the problem for a long time, months maybe. But other times the problem occurs the next day. This is happening with users who have established Outlook profiles as well as new users logging into their PCs for the first time. I've attached the code from our PRF. Any help is appreciated, as we have around 400 active users and we're constantly chasing after this issue.

That's a known issue from a few months back. I had the same problem. Something mucks up the Outlook database and it needs to be re-indexed. Do a Google search and you will find a fix. I think every user will have to do the fix.

Temp solution is stop or restart the service generally.

Have you configured your antivirus exclusions?
https://support.microsoft.com/en-gb/kb/823166

I've seen many exchange servers being stalled by antivirus locking files.

You often need to do it at the client end as well, depending on how you've configured exchange.

Couple steps you may apply...
 
1. Repair the offline file with a Microsoft utility called SCANOST.exe. I’ve seen this file reside in a number of different locations, mainly within Program Files. It might be best to search for it with Windows or Google Desktop. SCANPST.exe will also work, though you’ll have to go digging for your outlook.ost, which should be near c:\Documents and Settings\ %profile%\ Local Settings\ Application Data\ Microsoft\ Outlook\ outlook.ost. If your file is significant in size, you’ll save a lot of time with the repair operation by not creating a backup. Because if the repair finishes successfully and Outlook still bombs, you’ll need to.
2. Shutdown Outlook completely, including any runaway outlook.exe processes in the task manager. Open Mail in the Control Panel and before you delete your profile completely, write down the server settings! There’s no need to worry about backing up your mail as it’s stored on the Exchange server. (Essentially, you’re deleting that outlook.ost when you drop your mail profile.) Now, start Outlook and it will create a new profile, where you’ll configure the server with the information you wrote down previously.
 
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